Absorbent core for use in absorbent articles

ABSTRACT

An absorbent core includes a first carrier substrate and a second carrier substrate; a discontinuous layer of superabsorbent polymer material disposed between the first and second carrier substrates. The superabsorbent polymer material may be disposed in a plurality of superabsorbent material stripes. Two of the stripes are separated by an interstice. The interstice has little or no superabsorbent polymer material and extends from the first carrier substrate to the second carrier substrate.

FIELD OF THE INVENTION

The invention relates to absorbent cores having high amounts ofsuperabsorbent polymer material.

BACKGROUND OF THE INVENTION

The use of superabsorbent polymer material in disposable absorbentarticles, such as disposable diapers, is well known. The use ofsuperabsorbent polymer material facilitates absorbent articles having athinner absorbent core versus the use of absorbent materials such asfluff pulp (also referred to as airfelt), especially while the absorbentarticle is in the dry state.

In absorbent cores having a high percentage of superabsorbent polymermaterial and little or no airfelt (cellulose fibers) the superabsorbentpolymer material is often sandwiched between carrier substrates. Thecarrier substrates are typically nonwoven webs. The superabsorbentpolymer material needs to be immobilized between the carrier substratesto ensure that the superabsorbent polymer material does not migratewithin the absorbent core. Such immobilization is important both whenthe absorbent core is in the dry state as well as in use, when theabsorbent core gets wetted with liquids, such as urine. Immobilizationof the superabsorbent polymer material is often done with adhesives,such as hot melt adhesives. It is known to immobilize the superabsorbentpolymer material (which is typically in the form of superabsorbentpolymer particles) by applying adhesive in form of a fibrous network.The superabsorbent polymer material is thus adhered to the carriersubstrates as well as to each other. However, there is still a need forimproved immobilization of the superabsorbent polymer material to ensurethat expansion of the superabsorbent polymer materials upon liquidabsorption is not unduly restricted by the adhesive.

There is also a need for improved immobilization of the superabsorbentpolymer material to ensure that the expanded core upon liquid absorptiondoes not delaminate which might result in reduced superabsorbent polymermaterial immobilization and overall reduced integrity of the absorbentcore.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to an absorbent core comprising afirst carrier substrate and a second carrier substrate; and adiscontinuous layer of superabsorbent polymer material disposed betweenthe first and second carrier substrates. The discontinuous layer ofsuperabsorbent polymer material includes aplurality of superabsorbentmaterial stripes. Two of the stripes are separated by an interstice,wherein the interstice has little or no superabsorbent polymer materialand extends from the first carrier substrate to the second carriersubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a schematic drawing of a disposable diaper inaccordance with an embodiment of the invention

FIG. 2 is a schematic, partial cross sectional view of a laminateabsorbent core in accordance with an embodiment of the invention

FIG. 3 is a schematic, partial cross sectional view of another laminateabsorbent core in accordance with an embodiment of the invention

FIG. 4 is a schematic, partial cross sectional view of a laminateabsorbent core of the prior art

FIG. 5 is a schematic drawing of a Zwicker tensile tester.

FIG. 6 is a diagram showing pressure versus caliper as measured forExample 1 in the Laminate Compression Extension Test

FIG. 7 is a diagram showing pressure versus caliper as measured forComparative Example 1 in the Laminate Compression Extension Test

FIG. 8 is a diagram showing pressure versus caliper as measured forComparative Example 2 in the Laminate Compression Extension Test

DETAILED DESCRIPTION OF THE INVENTION Definitions

“Absorbent article” refers to devices that absorb and contain bodyexudates, and, more specifically, refers to devices that are placedagainst or in proximity to the body of the wearer to absorb and containthe various exudates discharged from the body. Absorbent articles mayinclude diapers, pants, training pants, adult incontinenceundergarments, sanitary napkin, and the like. As used herein, the term“body fluids” or “body exudates” includes, but is not limited to, urine,blood, vaginal discharges, breast milk, sweat and fecal matter.Preferred absorbent articles of the invention are diapers, pants,training pants and/or sanitary napkins.

“Absorbent core” means a structure that may be disposed between atopsheet and backsheet of an absorbent article for absorbing andcontaining liquid received by the absorbent article.

“Airfelt” is used herein to refer to comminuted wood pulp, which is aform of cellulose fibers (absorbent fibers).

“Diaper” refers to an absorbent article generally worn by infants andincontinent persons about the lower torso so as to encircle the waistand legs of the wearer and which is specifically adapted to receive andcontain urinary and fecal waste.

“Diaper-pant”, as used herein, refers to disposable garments having awaist opening and leg openings designed for infant or adult wearers. Adiaper-pant may be placed in position on the wearer by inserting thewearer's legs into the leg openings and sliding the pant into positionabout a wearer's lower torso. A diaper-pant may be preformed by anysuitable technique including, but not limited to, joining togetherportions of the article using refastenable and/or non-refastenable bonds(e.g., seam, weld, adhesive, cohesive bond, fastener, etc.). Adiaper-pant may be preformed anywhere along the circumference of thearticle (e.g., side fastened, front waist fastened). The terms“diaper-pant” is also commonly referred to as “prefastened diaper,”“pull-on diaper,” “training pant,” and “pant”.

“Disposable” is used in its ordinary sense to mean an article that isdisposed or discarded after a limited number of usage events overvarying lengths of time, for example, less than 10 events, less than 5events, or less than 2 events. A disposable absorbent article is mostoften disposed after single use.

“Hot melt adhesive” as used herein refers to adhesives in alignment withthe description given in “Adhesion and Adhesives Technology: AnIntroduction” by Alphonsus V. Pocius (Hanser publishers Munich, 1997).Therein a hot melt is defined as an adhesive applied from the melt andgaining strength upon solidification.

“Laminate absorbent core” as used herein refers to an absorbent corecomprising a first and second carrier substrate, and superabsorbentpolymer material placed between the first and second carrier substrate,wherein the superabsorbent polymer material is immobilized by a firstadhesive.

A “nonwoven web” is a manufactured sheet, web of directionally orrandomly orientated fibers, bonded by friction, and/or cohesion and/oradhesion, excluding paper and products which are woven, knitted, tufted,stitch-bonded incorporating binding yarns or filaments, or felted bywet-milling, whether or not additionally needled. The fibers may be ofnatural or man-made origin and may be staple or continuous filaments orbe formed in situ. Commercially available fibers have diameters rangingfrom less than about 0.001 mm to more than about 0.2 mm and they come inseveral different forms such as short fibers (known as staple, orchopped), continuous single fibers (filaments or monofilaments),untwisted bundles of continuous filaments, and twisted bundles ofcontinuous filaments (yarn). Nonwoven webs can be formed by manyprocesses such as meltblowing, spunbonding, solvent spinning,electrospinning, carding and airlaying. Nonwoven webs may be bonded byheat and/or pressure or may be adhesively bonded. Bonding may be limitedto certain areas of the nonwoven web (point bonding). Nonwoven webs mayalso be hydro-entangled or needle-punched. The basis weight of nonwovenwebs is usually expressed in grams per square meter (g/m²).

“Superabsorbent polymer material” as used herein refers to substantiallywater-insoluble polymer particles that can absorb at least 5 times theirweight of an aqueous 0.9% saline solution as measured using theCentrifuge Retention Capacity test (Edana 441.2-01). Preferredsuperabsorbent polymer materials are in the form of superabsorbentpolymer particles.

“Superabsorbent polymer particles” is used herein to refer to anabsorbent polymer material which is in particulate form so as to beflowable in the dry state.

Absorbent Article in the Form of a Diaper or Diaper-Pant

FIG. 1 is a plan view of a diaper 10 according to a certain embodimentof the invention. The diaper 10 is shown in its flat out, uncontractedstate (i.e. without elastic induced contraction) and portions of thediaper 10 are cut away to more clearly show the underlying structure ofthe diaper 10. A portion of the diaper 10 that contacts a wearer isfacing the viewer in FIG. 1. The diaper 10 generally may comprise achassis 12 and an absorbent core 14 disposed in the chassis 12.

The chassis 12 of the diaper 10 in FIG. 1 comprises the main body of thediaper 10. The chassis 12 may comprise an outer covering 16 including atopsheet 18, which may be liquid pervious, and/or a backsheet 20, whichmay be liquid impervious. The absorbent core 14 may be encased betweenthe topsheet 18 and the backsheet 20. The chassis 12 may also includeside panels 22, elasticized leg cuffs 24, and an elastic waist feature26.

The leg cuffs 24 and the elastic waist feature 26 may each typicallycomprise elastic members 28 such as elastic strands. One end portion ofthe diaper 10 is configured as a front waist region 30 of the diaper 10.An opposite end portion of the diaper 10 is configured as a back waistregion 32 of the diaper 10. An intermediate portion of the diaper 10 isconfigured as a crotch region 34, which extends longitudinally betweenthe first and second waist regions 30 and 32. The waist regions 30 and32 may include elastic elements such that they gather about the waist ofthe wearer to provide improved fit and containment (elastic waistfeature 26). The crotch region 34 is that portion of the diaper 10which, when the diaper 10 is worn, is generally positioned between thewearer's legs.

The diaper 10 is depicted in FIG. 1 with its longitudinal axis 36 andits transverse axis 38. The periphery 40 of the diaper 10 is defined bythe outer edges of the diaper 10 in which the longitudinal edges 42 rungenerally parallel to the longitudinal axis 36 of the diaper 10 and theend edges 44 run between the longitudinal edges 42 generally parallel tothe transverse axis 38 of the diaper 10. The diaper 10 may also includesuch other features as are known in the art including front and back earpanels, waist cap features, elastics and the like to provide better fit,containment and aesthetic characteristics.

In order to keep the diaper 10 in place about the wearer, at least aportion of the first waist region 30 may be attached by the fasteningmember 46 to at least a portion of the second waist region 32 to formleg opening(s) and an article waist. To this end, according to certainembodiments, the diaper 10 may be provided with a re-closable fasteningsystem or may alternatively be provided in the form of a diaper-pant.When the absorbent article is a diaper, it may comprise a re-closablefastening system joined to the chassis for securing the diaper to awearer. The fastening system may include at least one fastening member46 and at least one landing zone 48. When the absorbent article is adiaper-pant, the article may comprise two side panels on each waistregion 30, 32 joined to the chassis along the longitudinal edges of theside panels which face towards the longitudinal axis 36. The side panelsof the front waist region 30 are further joined to the respective sidepanels of the back waist region 32 along their longitudinal edges facingaway from the longitudinal axis 36 to form a pant.

Taking a cross section of FIG. 1 along the sectional line 2-2 of FIG. 1and starting from the wearer facing side, the diaper 10 may comprise thetopsheet 18, the components of the absorbent core 14, and the backsheet20. Diaper 10 may also comprise an acquisition system 50 disposedbetween the liquid permeable topsheet 18 and the wearer facing side ofthe absorbent core 14. The acquisition system 50 may be in directcontact with the absorbent core.

The acquisition system 50 may comprise a single layer or multiple layers(not shown), such as an upper acquisition layer facing towards thewearer and a lower acquisition layer facing the garment of the wearer.According to a certain embodiment, the acquisition system 50 mayfunction to receive a surge of liquid, such as a gush of urine. In otherwords, the acquisition system 50 may serve as a temporary reservoir forliquid until the absorbent core 14 can absorb the liquid.

In a certain embodiment, the acquisition system 50 may comprisechemically cross-linked cellulose fibers and/or nonwoven webs.

Absorbent Core

For the invention, absorbent cores with high amounts of superabsorbentpolymer material and low amounts of airfelt are analyzed in numerousrespects and compared to absorbent cores having relatively high amountsof airfelt mixed with superabsorbent polymer material. It has been foundthat in currently available absorbent cores with high amounts ofsuperabsorbent polymer material, fast liquid uptake in thesuperabsorbent polymer material is often inhibited to a certain extentas the superabsorbent polymer material is restricted from swelling uponfirst contact of the dry superabsorbent polymer material with liquid.Based on their findings, the inventors have found absorbent cores whichallow for improved liquid uptake.

The laminate absorbent core 14 comprises a first, lower laminate layer60 and a second, upper laminate layer 70. The first, lower laminatelayer 60 comprises a first carrier substrate 62 and the second, upperlaminate layer 70 comprises a second carrier substrate 72. Thesuperabsorbent polymer material 80 is applied onto each of the first andsecond carrier substrates 62 and 72 such that the superabsorbent polymermaterial 80 forms multiple stripes 90 on each of the first and secondcarrier substrates 62 and 72. On each of the carrier substrates 62 and72, the stripes of superabsorbent polymer material 90 are spaced apartfrom each other to form gaps 100 between neighboring stripes 90. Thegaps 100 between neighboring stripes 90 are substantially free ofsuperabsorbent polymer material 80. “Substantially free ofsuperabsorbent polymer material” means that e.g. due to process-relatedreasons, a small, negligible amount of superabsorbent polymer materialmay be present in the gaps, which however does not contribute to theoverall functionality. The term “substantially free of superabsorbentpolymer material” encompasses the term “free of superabsorbent polymermaterial”.

Before the first laminate layer 60 is joined to the second laminatelayer 70 to form the laminate absorbent core 14, a first adhesive 110 isapplied onto at least one of the first and second laminate layers 60 and70. In one embodiment, the first adhesive 110 is applied onto the firstand second laminate layer 60 and 70. The first adhesive 110 serves to atleast partially immobilize the superabsorbent polymer material 80 bothin dry and wet state. The first adhesive 110 is provided as a fibrouslayer which is at least partially in contact with the superabsorbentpolymer material 80 and partially in contact with the first and secondcarrier substrate 62 and 72. Typically, the first adhesive 110 forms afibrous network.

To form the laminate absorbent core 14, the first and second laminatelayer 60 and 70 are joined such that the first and second carriersubstrates 62 and 72 face outwardly. The first and second laminatelayers 60 and 70 are positioned on each other such that thesuperabsorbent polymer material stripes 90 of the second laminate layer70 are overlaying the gaps 100 formed in the first laminate layer 60 andthe superabsorbent polymer material stripes 90 of the first laminatelayer 60 are overlaying the gaps 100 formed in the second laminate layer70.

Each gap 100 in the first laminate layer 60 is wider than thecorresponding superabsorbent polymer material stripe 90 of the secondlaminate layer 70 lying above the gap 100. Also, each gap 100 in thesecond laminate layer 70 is wider than the corresponding superabsorbentpolymer material stripe 90 of the first laminate layer 60 lying belowthe gap 100. In the resulting laminate absorbent core 14, thesuperabsorbent polymer material 80 of the first laminate layer 60 doesnot contact the superabsorbent polymer material 80 of the secondlaminate layer 70 and vice versa. However, in embodiments wherein thegaps 100 between neighboring superabsorbent polymer material stripes 90in either laminate layer have a small, negligible amount ofsuperabsorbent polymer material due to process-related reasons and notcontributing to the overall functionality, those small amounts in thegaps may be in contact with the superabsorbent polymer material stripesof the respective other layer.

To ensure that, in the resulting laminate absorbent core 14, thesuperabsorbent polymer material 80 of the first laminate layer 60 doesnot contact the superabsorbent polymer material 80 of the secondlaminate layer 70 and vice versa, the superabsorbent polymer materialstripes 90 of one laminate layer may be positioned adjacent to the gaps100 of the respective other laminate layer such that the edge of thesuperabsorbent polymer material stripe 90 on the one laminate layer isspaced by at least 1 mm, or by at least 2 mm, or by at least 3 mm fromthe edge of the superabsorbent polymer material stripe 90 of the otherlaminate layer, which is positioned next to the respectivesuperabsorbent polymer material stripe 90 in the laminate absorbent core14 (indicated as 130 in FIGS. 2 and 3). This spacing 130 betweenneighboring superabsorbent polymer material stripes 90 of the laminateabsorbent core 14 (where a superabsorbent polymer material stripe 90 ofone laminate layer is neighboring a superabsorbent polymer materialstripe 90 of the respective other laminate layer) may not be more than10 mm or may not be more than 7 mm or may not be more than 5 mm. Thespacing 130 between neighboring superabsorbent polymer material stripes90 of the laminate absorbent core 14 may be such that the spacing 130 onboth sides of a superabsorbent polymer material stripe 90 is the same orthat the spacing 130 on one side is larger than the spacing of the otherside.

In the laminate absorbent core 14, the first adhesive 110 forms afibrous layer between the first and second laminate layer 60 and 70.

Once incorporated into an absorbent article 10 and in use of thearticle, the second, upper carrier substrate 72 is intended to be facingtowards the wearer and the first, lower carrier substrate 62 is intendedto be facing towards the garment. The second, upper carrier substrate 72may be a nonwoven web or may, alternatively, be a tissue. The first,lower carrier substrate 62 may be a nonwoven web, or may, alternativelybe a tissue or a film. In an embodiment where the first, lower carriersubstrate 62 is a film, the film may form at least part of thebacksheet, or may be in addition to the backsheet. The second, upper andfirst, lower carrier substrate 62 and 72 may be made of the samematerial or they may be made of different material (i.e. the secondcarrier substrate 72 may be a nonwoven web while the first carriersubstrate 62 may be a film). In embodiments wherein the second, upperand first, lower carrier substrate 62 and 72 are both nonwoven webs,these nonwoven webs may be the same nonwoven webs ore they may differfrom each other, e.g. with regard to their basis weight, hydrophilicity,air permeability or number and/or type of layers comprised by thenonwoven webs. The type of layers may be spunbonded layers or meltblownlayers. The nonwoven webs may also be carded webs made of staple fibers,and the carded webs may or may not comprise binder material. Thenonwoven webs may also be hydro-entangled or needle-punched.

Optionally, no nonwoven webs, tissues or films are provided between thefirst and second laminate layer 60 and 70.

The first and second carrier substrate 62 and 72 may be attached to eachother about their periphery to form an envelope about the superabsorbentpolymer material 80 comprised by the laminate absorbent core 14. Thefirst and second carrier substrate 62 and 72 may be attached to eachother with adhesive or any other means known in the art such asultrasonic bonding. In embodiments wherein the first and second carriersubstrate 62 and 72 are nonwoven webs, the first and second carriersubstrate may also be attached to each other by thermal and/or pressurebonding.

The first, lower carrier substrate 62 may be permeable or impermeablefor liquids, such as urine. The second, upper carrier substrate 72 maybe liquid permeable.

The laminate absorbent core 14 may comprise a second adhesive 115. Ifpresent, the second adhesive 115 is applied onto the first and/or secondcarrier substrate 62 and 72. There are different options for applyingthe second adhesive 115:

In one embodiment, the second adhesive 115 is applied onto the first andsecond carrier substrate 62 and 72 such that the second adhesive 115extends in the areas below the superabsorbent polymer material stripes90. In these embodiments, the second adhesive 115 has to be appliedbefore the superabsorbent polymer material stripes 90 are formed on thefirst and second carrier substrates 62 and 72. The second adhesive maybe applied on the whole surface of the first and/or second carriersubstrate but optionally is only applied in certain regions. The secondadhesive 115 can extend completely below the superabsorbent polymermaterial stripes 90. In any case, it is preferred that the secondadhesive 15 is provided in the gaps 100 formed between thesuperabsorbent polymer materials stripes 90.

Optionally, the second adhesive 115 is applied such that the secondadhesive forms stripes which are present at least in the gaps 100between neighboring superabsorbent polymer materials stripes 90 on thefirst and/or second carrier substrates 62 and 72. The stripes of secondadhesive 115 are separated from each other by gaps 116, which aresubstantially free of second adhesive. “Substantially free of secondadhesive” means that e.g. due to process-related reasons, a small,negligible amount of second adhesive may be present in the gaps, whichhowever does not contribute to the overall functionality. The term“substantially free of second adhesive” encompasses “free of secondadhesive”.

In embodiments wherein the second adhesive is applied in the form ofstripes, the second adhesive stripes 115 may or may not extend below theneighboring superabsorbent polymer material stripes 90. If the secondadhesive stripes 115 extend below the superabsorbent polymer materialstripes 90, the second adhesive stripes 115 will be wider than the gaps100 formed between neighboring superabsorbent polymer material stripes90. The second adhesive stripes 115 may extend below the superabsorbentpolymer stripes such that at least 5%, or at least 10%, or at least 20%or at least 50%, or at least 60%, of the area below the superabsorbentpolymer material stripes is covered by second adhesive 115. Moreover,the second adhesive stripes 115 may extend below the superabsorbentpolymer stripes such that less than 90%, or less than 75%, or less than50%, or less than 25%, or less than 15%, or less than 10%, or less than5% of the area below the superabsorbent polymer material stripes iscovered by second adhesive 115.

If the second adhesive stripes 115 do not extend below thesuperabsorbent polymer material stripes 90 (as illustrated in FIG. 3),the second adhesive stripes 115 may have a narrower width than the gaps100 formed between neighboring superabsorbent polymer material stripes90 or they may have the same width than the gaps 100 formed between thesuperabsorbent polymer material stripes 90.

The second adhesive can either be applied to form a fibrous layer or thesecond adhesive can be applied to cover the respective area of thecarrier substrate as a continuous, closed layer. Also when the secondadhesive is applied in the form of stripes, these stripes may be formedas a continuous, closed layer of second adhesive or as a stripe of fineadhesive fibers, which form a continuous network, or in otherconfigurations, such as rows of second adhesive spirals.

The second adhesive may be the same adhesive as the first adhesive ormay be different than the first adhesive. Optionally, the secondadhesive is a hot melt adhesive.

In the laminate absorbent core 14, the second adhesive 115 is at leastpartially in contact with the first adhesive 110 in the regions of thegaps 100 formed between the superabsorbent polymer material stripes 90.If the second adhesive 115 is applied on the first and second laminatelayer 60 and 70, the first adhesive 100 is at least partially in contactwith the second adhesive 115 on each of first and second laminate layers60 and 70 (also if the first adhesive has been initially applied only toone of the first and second laminate layers).

Each laminate layer 60 and 70 of the laminate absorbent core 14comprises multiple superabsorbent polymer material stripes 90. Thenumber of superabsorbent polymer material stripes in each of the firstand second laminate layer is at least 2. The number of superabsorbentpolymer material stripes in each laminate layer may be at least 3 or 4and may be less than 8 or may be less than 7 or less than 6. One of thelaminate layers may have one superabsorbent polymer material stripe morethan the respective other laminate layer.

The average basis weight of the superabsorbent polymer material in thesuperabsorbent polymer material stripes may be from 150 g/m² to 700g/m², or from 200 g/m² to 600 g/m², or from 250 g/m² to 500 g/m². Thebasis weight of the superabsorbent polymer material may differ along thelength of the superabsorbent polymer material stripe. Also, the basisweight of the superabsorbent polymer material may differ along the widthof the superabsorbent polymer material stripe. This may especially bethe case when the superabsorbent polymer material is applied in theshape of little humps, given the superabsorbent polymer material isflowable (especially when the superabsorbent polymer material is in theform of superabsorbent polymer particles). The average basis weight ofthe superabsorbent polymer material may also be different for differentstripes comprised by the laminate absorbent core.

The basis weight of superabsorbent polymer material may or may not varyalong the length of the laminate absorbent core. Often the core isprofiled in its longitudinal direction. It has been found that, for mostabsorbent articles such as diapers, the liquid discharge occurspredominately in the front half of the diaper. The front half of thelaminate absorbent core should therefore comprise most of the absorbentcapacity of the core. Thus, according to certain embodiments, the fronthalf of the laminate absorbent core 14 may comprise more than about 60%of the superabsorbent polymer material, or more than about 65%, 70%,75%, 80%, 85%, or 90% of the superabsorbent polymer material based onthe total superabsorbent polymer material provided in the laminateabsorbent core. The average basis weight of the superabsorbent polymermaterial comprised by the laminate absorbent core may be from 100 g/m²to 500 g/m², or from 150 g/m² to 400 g/m² based on the surface area ofthe laminate absorbent core (i.e. the areas of the stripes ofsuperabsorbent polymer material and of the gaps between these stripes).The surface area of the laminate absorbent core is defined by the x- andy-dimension of the laminate absorbent core. Any potential unevenness ofthe surface and irregularities of thickness (i.e. in the z-direction) isnot taken into account. The x-,y-dimension of the laminate absorbentcore is determined while the laminate absorbent core is lying flat on atable with not stress or strain applied (this also applies forpotentially extensible absorbent cores). If needed, elasticallycontracting elements that otherwise would apply strain to the laminateabsorbent core can be carefully removed prior to lying the laminateabsorbent core flat on a table.

The superabsorbent polymer material stripes may be straight or they maytake any other shape, such as curved, wavy or spiraled, though straightor curved superabsorbent polymer material stripes are preferred. Theshape of the superabsorbent polymer material stripe may also bedifferent for different stripes.

The width of one or more of the superabsorbent polymer material stripesin the laminate absorbent core may also vary along its length. Also,alternatively or in addition to a varying width of an individualsuperabsorbent polymer material stripe, different superabsorbent polymermaterial stripes of the laminate absorbent core may also have differentwidth.

The width of each of the superabsorbent polymer material stripes may beat least 5 mm, or at least 10 mm, or at least 15 mm, or at least 20 mm,or at least 25 mm. The maximum width of the superabsorbent polymermaterial stripes will depend on the dimensions of the laminate absorbentcore and the number of superabsorbent polymer materials stripes. Thewidth of the superabsorbent polymer stripes may be less than 50 mm, orless than 40 mm or less than 30 mm. The gaps between the superabsorbentpolymer material stripes within one laminate layer may have a width ofgreater than 6 mm, or greater than 11 mm, or greater than 16 mm, orgreater than 21 mm, or greater than 26 mm. The gaps between thesuperabsorbent polymer material stripes within one laminate layer mayhave a width of not more than 52 mm, or not more than 42 mm, or not morethan 32 mm.

The gaps 100 between the superabsorbent polymer material stripes 90 oneach laminate layer is wider than the width of the superabsorbentpolymer material stripe 90 of the respective other laminate layer, whichis laying on top or below the respective gap. The width of the gap 100may be at least 2 mm wider than the width of the respectivesuperabsorbent polymer material stripe 90 which is lying beneath orabove the respective gap 100. The width of the gap 100 betweenneighboring superabsorbent polymer material stripes 90 may be at least 3mm wider or at least 4 mm wider than the width of the respectivesuperabsorbent polymer material stripe 90 which is lying beneath orabove the respective gap 100. The width of the gap 100 betweenneighboring superabsorbent polymer material stripes 90 may be not morethan 15 mm, or not more than 10 mm, or not more than 8 mm wider than thewidth of the respective superabsorbent polymer material stripe 90 whichis lying beneath or above the respective gap 100.

When the second adhesive, if present, is applied in stripes 115 withinthe gaps 100 between neighboring superabsorbent polymer materialsstripes 90, the second adhesive stripes 115 may have a width of at least1 mm or at least 2 mm or at least 3 mm or at least 4 mm. The width ofthe second adhesive stripe 115 may be less than 20 mm or less than 10 mmor less than 5 mm or less than 3 mm.

The laminate absorbent core 14 has a longitudinal direction (the lengthof the laminate absorbent core) with a longitudinal axis and a lateraldirection (the width of the absorbent core) with a lateral axis. Thelongitudinal direction will generally be wider than the lateraldirection. Also, the longitudinal direction is perpendicular to thelateral direction. When put in an absorbent article, the longitudinalaxis of the laminate absorbent core is substantially parallel to thelongitudinal axis of the absorbent article and the lateral axis of thelaminate absorbent core is substantially parallel to the lateral axis ofthe absorbent article. “Substantially parallel” means that slightdeviations, e.g. of up to 10° may occur. In one embodiment, thelongitudinal axis of the laminate absorbent core is parallel to thelongitudinal axis of the absorbent article and the lateral axis of thelaminate absorbent core is parallel to the lateral axis of the absorbentarticle.

The laminate absorbent core further has a front region, a back regionand a crotch region therein between and a front lateral edge, anopposing back lateral edge, and longitudinally extending side edges.

The front zone of the laminate absorbent core represents one third ofthe laminate absorbent core extending from the front edge of thelaminate absorbent core along the longitudinal axis towards the crotchregion. Once placed in an absorbent article, the front zone of thelaminate absorbent core is placed towards the front waist edge of theabsorbent article. The back zone represents one third of the laminateabsorbent core extending from the back edge along the longitudinal axistowards the crotch region. Once put in an absorbent article, the backzone of the laminate absorbent core is placed towards the back waistedge of the absorbent article. The crotch zone represents the remainingthird of the laminate absorbent core and extends between the front zoneand the back zone. The complete length of the laminate absorbent core isdefined as longest extension of the laminate absorbent core along orparallel to the longitudinal axis of the laminate absorbent core. Theabsorbent core of the invention may be rectangular. However, thelaminate absorbent core may also take any other shape. In oneembodiment, the crotch region of the laminate absorbent core has anarrower width than the front and back regions of the absorbent core.The shape of the laminate absorbent core of the invention is optionallyaxially symmetric with regard to the longitudinal axis of the laminateabsorbent core. The shape of the laminate absorbent core of theinvention may also be axially symmetric with regard to the lateral axisof the laminate absorbent core.

The laminate absorbent core of the invention may have a caliper of atleast 1 mm, or at least 2 mm, or at least 3 mm. The caliper may be lessthan 20 mm, or less than 15 mm, or less than 10 mm, or less than 8 mm,or less than 5 mm. The caliper of the laminate absorbent core ismeasured at the point where the longitudinally axis crosses the lateralaxis of the laminate absorbent core with no forces being applied on thelaminate absorbent core (i.e. the laminate absorbent is neithercompressed nor torn apart).

The superabsorbent polymer material stripes may extend in thelongitudinal direction of the laminate absorbent core. Though lesspreferred, the superabsorbent polymer material stripes may alternativelyextend in the lateral direction of the laminate absorbent core.

It is preferred that the superabsorbent polymer material stripes extendalong the complete laminate absorbent core (for both options,longitudinally and laterally extending superabsorbent polymer materialstripes). However the superabsorbent material stripes may also extendalong only a part of the laminate absorbent core, such as not more than90%, or not more than 75%, or not more than 50%, or not more than 25% ofthe longitudinal direction of the laminate absorbent core. Thesuperabsorbent material stripes may extend along at least 50%, or atleast 75% or at least 90% of the longitudinal direction of the laminateabsorbent core. The superabsorbent polymer material stripes may alsoextend along not more than 90%, or not more than 75%, or not more than50%, or not more than 25% of the lateral direction of the laminateabsorbent core. The superabsorbent material stripes may extend along atleast 50%, or at least 75% or at least 90% of the lateral direction ofthe laminate absorbent core.

For embodiments, wherein the superabsorbent polymer material stripes doextend only along a part of the longitudinal or lateral direction of thelaminate absorbent core, the stripes may not extend to any of thelateral or longitudinal side edges of the absorbent core.

The first, lower carrier substrate 62 of the laminate absorbent core 14is facing towards the garment when the laminate absorbent core 14 is putin an absorbent article 10, such as a diaper or diaper-pant. The second,upper carrier substrate 72 is facing towards the wearer once thelaminate absorbent core 14 is put in an absorbent article 10. Generally,the laminate absorbent core 10 is placed between the topsheet 18 and thebacksheet 20 of the absorbent article 10. In absorbent articles whichcomprise a fluid acquisition system 50, the laminate absorbent core 14is typically placed below the fluid acquisition system 50. However, itmay alternatively be desirable to place the fluid acquisition systembelow the laminate absorbent core in an absorbent article.

The laminate absorbent core comprises absorbent material such assuperabsorbent polymer material or airfelt (comprising cellulosefibers). The absorbent materials are contained within an upper and alower carrier substrate.

The laminate absorbent core may be substantially free of absorbentmaterial other than superabsorbent polymer material. For example, theabsorbent material may comprise more than 80% by weight, optionally morethan 90% by weight, more optionally more than 95% by weight and evenmore optionally more than 98% by weight of superabsorbent polymermaterial. In one embodiment all of the absorbent material comprised bythe absorbent core is superabsorbent polymer material. If the laminateabsorbent core comprises cellulose fiber (also sometimes referred to as“wood pulp”, “fluff pulp” or “airfelt”) in addition to thesuperabsorbent polymer material, the laminate absorbent core maycomprise less than 5% by weight of cellulose fibers. Also, the cellulosefibers are optionally not provided in the gaps between neighboringsuperabsorbent polymer material stripes.

Superabsorbent Polymer Material

The superabsorbent polymer material will typically be in the form ofsuperabsorbent polymer particles. The superabsorbent polymer particlesmay be of numerous shapes. The term “particles” refers to granules,fibers, flakes, spheres, powders, platelets and other shapes and formsknown to persons skilled in the art of superabsorbent polymer particles.E.g. the particles can be in the form of granules or beads, having aparticle size from about 10 μm to about 1000 μm, optionally from about100 μm to about 1000 μm, even more optionally from about 150 μm to about850 μm and most optionally from about 150 μm to about 500 μm. In anotherembodiment, the superabsorbent polymer particles can be in the shape offibers, i.e. elongated, acicular superabsorbent polymer particles. Inthose embodiments, the superabsorbent polymer fibers have a minordimension (i.e. diameter of the fiber) of less than about 1 mm, usuallyless than about 500 μm, and optionally less than 250 μm down to 50 μm.The length of the fibers is optionally about 3 mm to about 100 mm. Thefibers can also be in the form of a long filament that can be woven.

Preferred superabsorbent polymer particles of the invention arespherical-like particles. According to the invention and in contrast tofibers, “spherical-like particles” have a longest and a smallestdimension with a particulate ratio of longest to smallest particledimension in the range of 1-5, where a value of 1 would equate aperfectly spherical particle and 5 would allow for some deviation fromsuch a spherical particle.

The superabsorbent polymer materials useful in the invention include avariety of water-insoluble, but water-swellable polymers capable ofabsorbing large quantities of fluids. Such polymers materials aregenerally known in the art and include all those well-known polymersused or deemed useful in the context of disposable absorbent articletechnology.

Preferred polymer materials for use in making superabsorbent polymermaterials are slightly network cross linked polymers of partiallyneutralized polyacrylic acids and starch derivatives thereof.Starch-based superabsorbent polymer materials are also encompassed inthe invention. Optionally, the superabsorbent polymer materials comprisefrom 25% to 95% by weight, more optionally from 50% to 80% by weightneutralized, slightly network cross-linked, polyacrylic acid. Networkcross-linking renders the polymer substantially water-insoluble and, inpart, determines the absorptive capacity and extractable polymer contentcharacteristics of the superabsorbent polymer material.

While the superabsorbent polymer materials is optionally of one type(i.e., homogeneous), mixtures of polymers can also be used in theinvention. The superabsorbent polymer materials can also comprisemixtures with low levels of one or more additives, such as for examplepowdered silica, surfactants, adhesive, binders, and the like.Furthermore, the superabsorbent polymer particles can comprise agradient in particle size or can comprise a certain range of particlesize.

Many of the formerly known superabsorbent polymer particles exhibitedgel blocking. “Gel blocking” occurs when particles made of thesuperabsorbent polymer materials are wetted and the particles swell soas to inhibit fluid transmission to other zones or regions of theabsorbent structure. Wetting of these other regions of the absorbentcore therefore takes place via a very slow diffusion process. Inpractical terms, this means acquisition of fluids by the absorbentstructure is much slower than the rate at which fluids are discharged,especially in gush situations. Leakage from the absorbent article cantake place well before the particles of superabsorbent polymer materialsin the absorbent core are even close to being fully saturated or beforethe fluid can diffuse or wick past the “blocking” particles into therest of the absorbent core.

One commonly applied way to reduce gel blocking is to make the particlesstiffer, which enables the superabsorbent polymer particles to retaintheir original shape thus creating or maintaining void spaces betweenthe particles. A well-known method to increase stiffness is tocovalently and/or ionically cross-link the carboxyl groups exposed onthe surface of the superabsorbent polymer particles. This method iscommonly referred to as surface cross-linking.

First and Second Adhesive

The first and optional second adhesive comprised by the laminateabsorbent core is optionally a hot melt adhesive. In certain,non-preferred embodiments, the first adhesive is a hot melt adhesivewhereas the second adhesive may be another type of adhesive. The averagebasis weight of first plus optional second adhesive in the laminateabsorbent core may be from 2 g/m² to 20 g/m², or from 2 g/m² to 10 g/m²based on the surface area of the laminate absorbent core. The averagebasis weight of the first adhesive alone in the laminate absorbent coremay be from 1 g/m² to 18 g/m², or from 2 g/m² to 15 g/m² based on thesurface area of the laminate absorbent core.

The first adhesive serves to at least partially immobilize thesuperabsorbent polymer material of the laminate absorbent core, both indry and wet condition.

Without wishing to be bound by theory, it has been found that those hotmelt adhesives which are most useful for immobilizing the superabsorbentpolymer material combine good cohesion and good adhesion behavior. Goodadhesion may promote good contact between the hot melt adhesive and thesuperabsorbent polymer material and the carrier substrates. Goodcohesion reduces the likelihood that the adhesive breaks, in particularin response to external forces, and namely in response to strain. Whenthe laminate absorbent core absorbs liquid, the superabsorbent polymermaterial swells and subjects the hot melt adhesive to external forces.The hot melt adhesive may allow for such swelling, without breaking andwithout imparting too many compressive forces, which would restrain theabsorbent particulate polymer material from swelling.

In accordance with one embodiment of the invention the hot melt adhesivemay comprise, in its entirety, a single thermoplastic polymer or a blendof thermoplastic polymers, having a softening point, as determined bythe ASTM Method D-36-95 “Ring and Ball”, in the range between 50° C. and300° C., or alternatively the hot melt adhesive may comprise at leastone thermoplastic polymer in combination with other thermoplasticdiluents such as tackifying resins, plasticizers and additives such asantioxidants.

In certain embodiments, the thermoplastic polymer typically has a weightaverage molecular weight (Mw) of more than 10,000 and a glass transitiontemperature (Tg) usually below room temperature (25° C.), or of lessthan 22° C., or less than 18° C., or less than 15° C. In certainembodiments Tg may be above 0° C.>Tg. In embodiments where thethermoplastic polymer has more than one Tg the values given refer to thelowest glass transition temperature. The thermoplastic polymer may alsohave a softening point, as determined by the ASTM Method D-36-95 “Ringand Ball”, in the range between 50° C. and 300° C. In some embodimentsthe Mw of the thermoplastic polymer is less than 10000000.

In certain embodiments, typical concentrations of the thermoplasticpolymer in a hot melt adhesive are in the range of about 20% to about40% by weight of the hot melt adhesive.

Exemplary polymers are (styrenic) block copolymers including A-B-Atriblock structures, A-B diblock structures and (A-B)n radial blockcopolymer structures wherein the A blocks are non-elastomeric polymerblocks, typically comprising polystyrene, and the B blocks areunsaturated conjugated diene or (partly) hydrogenated versions of such.The B block is typically isoprene, butadiene, ethylene/butylene(hydrogenated butadiene), ethylene/propylene (hydrogenated isoprene),and mixtures thereof.

Other suitable thermoplastic polymers that may be employed aremetallocene polyolefins, which are ethylene polymers prepared usingsingle-site or metallocene catalysts. Therein, at least one comonomercan be polymerized with ethylene to make a copolymer, terpolymer orhigher order polymer. Also applicable are amorphous polyolefins oramorphous polyalphaolefins (APAO) which are homopolymers, copolymers orterpolymers of C2 to C8 alpha olefins.

In exemplary embodiments, the tackifying resin has typically a Mw below5,000 and a Tg usually above room temperature (25° C.), typicalconcentrations of the tackifying resin in a hot melt are in the range ofabout 30% to about 60% by weight of the hot melt adhesive. In certainembodiments the tackifying resin has an Mw of more than 1,000.

The plasticizer has a low Mw of typically less than 1,000 and a Tg belowroom temperature, with a typical concentration of about 0% to about 15%by weight of the hot melt adhesive. In certain embodiments theplasticizer has an Mw of more than 100.

In certain embodiments, the first and/or second adhesive is hot meltadhesive present in the form of fibers. In some embodiments, the fiberswill have an average thickness of about 1 to about 50 micrometers orabout 1 to about 35 micrometers and an average length of about 5 mm toabout 50 mm or about 5 mm to about 30 mm.

Method of Making the Laminate Absorbent Core

One method of making the laminate absorbent core comprises the followingsteps: A first and a second carrier substrate are provided. Onto each ofthe first and second carrier substrate, multiple stripes ofsuperabsorbent polymer material are formed. The stripes are formed suchthat neighboring stripes are separated by gaps.

After the stripes of superabsorbent polymer material are formed, a firstadhesive is applied in the form of a fibrous layer on at least one ofthe first and second carrier substrates. In one embodiment, the firstadhesive is applied on the first and second carrier substrate.

The first carrier substrate with the superabsorbent polymer materialstripes formed thereon and the optional first adhesive applied on thesestripes constitutes a first laminate layer and the second carriersubstrate with the superabsorbent polymer material stripes formedthereon and the optional first adhesive applied on these stripesconstitutes a second laminate layer.

Thereafter, the first and second laminate layers are combined to form alaminate absorbent core. The first and second carrier substrates arecombined such the superabsorbent polymer material stripes face inwardly.The superabsorbent polymer material stripes on one carrier substrate areoverlaying the gaps of the other carrier substrate and each gap on thefirst carrier substrate is wider than the corresponding superabsorbentpolymer material stripe on the second carrier substrate, and also eachgap on the second carrier substrate is wider than the correspondingsuperabsorbent polymer material stripe on the first carrier substrate.

In embodiments, wherein the first adhesive is only applied onto one ofthe first or second carrier substrates, it is preferred that thelaminate layer having no first adhesive applied thereon is lyinghorizontally flat while the respective other laminate layer having thefirst adhesive applied is placed on top of the carrier substrate withoutfirst adhesive. The superabsorbent polymer material stripes of thecarrier substrate having no first adhesive provided thereon may be heldin place by vacuum, which is applied below the carrier substrate.

An alternative method of making the laminate absorbent core comprisesthe steps of

-   -   providing a first carrier substrate;    -   forming a first set of multiple stripes of superabsorbent        polymer material on the first carrier substrate such that the        stripes are spaced apart from each other to form gaps between        neighboring stripes;    -   applying a first adhesive in the form of a fibrous layer on the        first carrier substrate on the surface comprising the        superabsorbent polymer material stripes;    -   forming a second set of multiple stripes of superabsorbent        polymer material on the fibrous layer of the first adhesive, the        second set of multiple stripes of superabsorbent polymer        material being spaced apart from each other to form gaps between        neighboring stripes;    -   applying a second carrier substrate on top of the second set of        superabsorbent polymer material stripes.

The first and second set of multiple stripes of superabsorbent polymermaterial are arranged such that the superabsorbent polymer materialstripes of one set are overlaying the gaps of the superabsorbent polymermaterial stripes of respective other set. Each gap in the first set ofsuperabsorbent polymer material stripes is wider than the correspondingsuperabsorbent polymer material stripe of the second set ofsuperabsorbent polymer material stripes, and each gap in the second setof superabsorbent polymer material stripes is wider than thecorresponding superabsorbent polymer material stripe of the first set ofsuperabsorbent polymer material stripes.

In this alternative method, the first carrier substrate, the first setof multiple stripes of superabsorbent polymer material and the firstadhesive together are considered to form a first laminate layer. Thesecond carrier substrate together with the second set of multiplestripes of superabsorbent polymer material forms a second laminatelayer.

For both methods, the following applies:

The number of superabsorbent polymer material stripes in each of thelaminate layers may be from 3 to 8, or from 4 to 6.

The width of each of the superabsorbent polymer material stripes may beat least 5 mm, or at least 10 mm, or at least 15 mm, or at least 20 mm,or at least 25 mm. The maximum width of the superabsorbent polymermaterial stripes will depend on the dimensions of the laminate absorbentcore and the number of superabsorbent polymer materials stripes. Thewidth of the superabsorbent polymer material stripes may be less than 50mm, or less than 40 mm or less than 30 mm. The gaps between thesuperabsorbent polymer material stripes within one laminate layer mayhave a width of greater than 6 mm, or greater than 11 mm, or greaterthan 16 mm, or greater than 21 mm, or greater than 26 mm. The gapsbetween the superabsorbent polymer material stripes within one laminatelayer may have a width of not more than 52 mm, or not more than 42 mm,or not more than 32 mm.

The width of the gap in one laminate layer may be at least 2 mm widerthan the width of the superabsorbent polymer material stripe of theother laminate layer, which is lying on top or below the respective gap.The width of the gap between neighboring superabsorbent polymer materialstripes may be at least 3 mm wider or at least 4 mm wider than the widthof the respective superabsorbent polymer material stripe which is lyingbeneath or above the respective gap. The width of the gap betweenneighboring superabsorbent polymer material stripes may be not more than15 mm, or not more than 10 mm, or not be more than 8 mm wider than thewidth of the respective superabsorbent polymer material stripe which islying beneath or above the respective gap.

To ensure that in the resulting laminate absorbent core thesuperabsorbent polymer material of the first laminate layer does notcontact the superabsorbent polymer material of the second laminate layerand vice versa, the superabsorbent polymer material stripes of onelaminate layer may be positioned adjacent to the gaps of the respectiveother laminate layer such that the edge of the superabsorbent polymermaterial stripe on the one laminate layer is spaced by at least 1 mm, orby at least 2 mm, or by at least 3 mm from the edge of thesuperabsorbent polymer material stripe of the other laminate layer,which is positioned next to the respective superabsorbent polymermaterial stripe in the laminate absorbent core. This spacing betweenneighboring superabsorbent polymer material stripes of the finallaminate absorbent core (where a superabsorbent polymer material stripeof one layer is neighboring a superabsorbent polymer material stripe ofthe respective other layer) may not be more than 10 mm or may not bemore than 7 mm or may not be more than 5 mm, or may not be more than 3mm. The spacing between neighboring superabsorbent polymer materialstripes of the laminate absorbent core may be such that the spacing onboth sides of a superabsorbent polymer material stripe is the same orthat the spacing on one side is larger than the spacing of the otherside.

Both methods may also comprise a step of applying a second adhesive ontothe first and/or second carrier substrate such that the second adhesiveis applied at least in the gaps between the superabsorbent polymermaterial stripes. The second adhesive may also be applied below thesuperabsorbent polymer material stripes of the respective laminatelayer. The optional second adhesive should be applied such that, in thelaminate absorbent core, the first adhesive is in contact with thesecond adhesive of the first and/or second carrier substrate in theregions of the gaps between the superabsorbent polymer material stripes.

The optional second adhesive may be applied in the form of multiplestripes on at least one of the first and second carrier substrates suchthat, in the laminate absorbent core, the first adhesive is in contactwith the second adhesive, and wherein the second adhesive stripes extendbelow the neighboring superabsorbent polymer material stripes of therespective laminate layer by at least 1% and by less than 50% of widthof the neighboring superabsorbent polymer material stripe.Alternatively, the second adhesive stripes do not extend belowneighboring superabsorbent polymer material stripes but the secondadhesive stripes are only applied in the gaps between the superabsorbentpolymer material stripes. The second adhesive stripes may have a widthof at least 1 mm or at least 2 mm or at least 3 mm or at least 4 mm. Thewidth of the second adhesive stripes may be less than 20 mm or less than10 mm or less than 5 mm or less than 3 mm.

The second carrier substrate may be a nonwoven web or may,alternatively, be a tissue. The first, carrier substrate may be anonwoven web, or may, alternatively be a tissue or a film. If the firstcarrier substrate is a film, this carrier substrate should be facingtowards the garment facing surface of an absorbent article while thesecond carrier substrate should be facing towards the wearer-facingsurface of the absorbent article, once the laminate absorbent core isincorporated into an absorbent article.

In both methods of making the laminate absorbent core, less than 5% byweight of cellulose fibers based on the total weight of the laminateabsorbent core may be comprised in the resulting laminate absorbentcore.

In both methods of making the laminate absorbent core, the first andsecond carrier substrates may be provided on a supporting substrate,such as a conveyor belt. Below the supporting substrate, a vacuum may beapplied to ensure that the carrier substrates are sufficientlyimmobilized on the supporting substrates.

The supporting substrate may also be in the form of a drum. In suchembodiments, the first and second carrier substrates may be held inplace on the surface of the supporting drum by and underlying vacuum.

In the method wherein the first laminate layer and the second laminatelayer are formed independently from each other and are joined to eachother after being formed, the first carrier substrate may be provided ona first drum and the second carrier substrate may be provided on asecond drum until the moment, in which the first and second laminatelayers are combined with each other. Upon combining the first laminatelayer with the second laminate layer, the resulting laminate absorbentcore may be provided on either the first or second drum or may,alternatively, be provided on a third drum or other supportingsubstrate, such as a conveyor belt. The resulting laminate absorbentcore may also be directly placed on other components of an absorbentarticle, such as the backsheet, acquisition system or topsheet, or on acombination of the topsheet and the acquisition system.

All other optional features and components set out above with regard tothe laminate absorbent core and its first and second laminate layers areequally applicable to the methods of manufacturing the laminateabsorbent core.

Laminate Compression Extension

To simulate closely the forces which occur when the superabsorbentpolymer material within the laminate absorbent core swells and expandsupon absorption of liquid, leading to a general expansion of thelaminate absorbent core, the laminate absorbent core is subjected to theLaminate Compression Extension Test as described in detail below.

In this test, a dry laminate absorbent core is pulled apart in thez-direction of the absorbent core and the force is measured, which isrequired to pull the laminate absorbent core apart and the pressure,which the laminate absorbent core exerts upon being pulled apart.

As Comparative Example 1 (see below), the absorbent core of Pampers“Active Fit”, Size 4 as commercially available in Germany in May 2011,which is a disposable diaper having a laminate absorbent core with noairfelt (cellulose fibers) has been subjected to the LaminateCompression Extension Test.

In the laminate absorbent core of Pampers “Active Fit”, thesuperabsorbent polymer material is provided in two layers within anupper and a lower nonwoven carrier substrate. The superabsorbent polymermaterial is immobilized between the upper and lower nonwoven web by ahot melt adhesive in the form of a fibrous layer, which is appliedbetween the superabsorbent polymer material of the upper laminate layerand the superabsorbent polymer material of the lower laminate layer.

It has been found that the force required to pull such a laminateabsorbent core apart steeply increases for the initial phase of pulling.After the laminate absorbent core has been pulled apart slightly (about1 to 3 mm), the force required to pull the laminate absorbent corefurther apart quickly decreases to an extent that only relatively smallforces are needed to pull the laminate absorbent core further apart.

Considering a situation, wherein such a laminate absorbent core isplaced in an absorbent article, such as a disposable diaper, thisfinding suggests, that upon the initial absorption of liquid, fastexpansion of the superabsorbent polymer material comprised in thelaminate absorbent core is hindered to a certain extent. This may resultin delayed absorption of liquid, increasing the risk of diaper leakage.

Without wishing to be bound by theory, it is believed that therelatively high amount of forces which need to be applied upon initialexpansion of the laminate absorbent core in the z-direction (i.e. in thethickness direction of the absorbent core), might be due to thestructure of the fibrous network of adhesive material applied betweenthe upper and lower laminate layers.

In the currently available laminate absorbent cores having little or noairfelt between the upper and lower carrier substrates, thesuperabsorbent polymer material is applied such that a generallycontinuous layer of superabsorbent polymer material is provided. Thiscan be achieved for example by applying superabsorbent polymer materialin a discontinuous manner in the individual upper and lower laminatelayer (such as in the form of “islands” of superabsorbent polymermaterial which are at least partly surrounded by areas with nosuperabsorbent polymer material) and combining the upper and lowerlaminate layer in a way that the superabsorbent polymer material isprovided generally continuous between the upper and lower carriersubstrates. In such embodiments, the “islands” of superabsorbent polymermaterials in the respective layers overlap each other to a certainextent upon combining the upper and lower layer together. Such anembodiment of the prior art is shown in FIG. 4.

At least part of the adhesive (the first adhesive) is applied as anadhesive fibrous network between the upper and lower laminate layers,that is, an adhesive fibrous layer is provided on top of thesuperabsorbent polymer material of each layer immediately prior tocombining the upper and lower laminate layer. Upon joining the upper andlower laminate layer together, it is believed that in the course of thiscombination, at least a part of the adhesive fibers comprised in onelaminate layer stick to at least a part of the adhesive fibers of therespective other laminate layer (shown in FIG. 4). In such laminateabsorbent cores of the prior art few adhesive fibers of an adhesivefibrous network initially applied on one laminate layer are believed toextend all the way through the thickness of the absorbent laminate corefrom one carrier substrate to the other, being adhered to both, theupper and lower carrier substrate. Instead, an adhesive fiber of theadhesive fibrous network of one laminate layer may be attached to thecarrier substrate of this laminate layer and may extend from the carriersubstrate through a part of the thickness of the absorbent core where itis stuck to an adhesive fiber of the adhesive fibrous network of theother laminate layer. Vice versa, an adhesive fiber of the adhesivefibrous network of the respective other laminate layer may be attachedto the carrier substrate of this other laminate layer and may extendfrom the this carrier substrate through a part of the thickness of theabsorbent core where it is stuck to an adhesive fiber of the adhesivefibrous network of the other laminate layer. Hence, relatively manyadhesive fibers of the fibrous network of one laminate layer may adhereto adhesive fibers of the fibrous network of the respective otherlaminate layer.

Also, few adhesive fibers may extend from the upper carrier substratebetween the particles of the superabsorbent polymer materials onto thelower carrier substrate (i.e. these fibers are adhered to the upper andlower carrier substrate). However, as the superabsorbent polymermaterial is applied substantially continuously in the laminate absorbentcore between the upper and lower carrier substrate, the adhesive fibersextending from the upper carrier substrate onto the lower carriersubstrate and being adhered to the upper and lower carrier substrate are“squeezed” between the superabsorbent polymer material and will thusspan a relatively short distance, i.e. they will take a short pathdefined by a relatively straight line between the upper and lowerlaminate layer. Hence, upon expansion of the laminate absorbent core inthe z-direction, these adhesive fibers have to elongate to be able tofollow expansion without breaking. Since the adhesive fibers typicallyhave certain elastic properties, elongation of the adhesive fibers isgenerally possible. However, elongation of adhesive fibers requires acertain amount of force. This theory is supported by the finding thatwhen a sample derived from a Pampers Active fit diaper (ComparativeExample 1) is subjected to the Laminate Compression Extension Test, theinitial force needed to separate the laminate absorbent core in thez-direction is relatively high (see graph in FIG. 7).

Furthermore, while the adhesive fibrous network is initially appliedonto the superabsorbent polymer material of a laminate layer at hightemperature and thus in a state of relatively low viscosity, thetemperature of the adhesive fibrous network will have decreased to acertain extent when the upper and lower laminate layer are joined toeach other. Even if the step of joining the laminate layers to eachother takes place immediately after step of applying the adhesivefibrous network, the adhesive fibrous network will have cooled down to acertain extent compared to the temperature, at which the adhesive wasapplied on the laminate layer, especially given the adhesive fibers havehigh surface area compared to their volume, which promotes fasttemperature drop. As the temperature of the adhesive fibrous network islowered, the viscosity of the fibrous network increases. As aconsequence, the adhesive fibers of the upper laminate layer, whencoming into contact with the adhesive fibers of the lower laminatelayer, will not be able to form a joint that is as stable as theintegral adhesive fibrous network applied on the respective laminatelayers. Consequently, the contact areas between the first, lower andsecond, upper fibrous network are more prone to separation upon pullingthe laminate absorbent core apart in the z-direction compared toseparation of the adhesive fibers within an adhesive fibrous network ofa given laminate layer. Such tendency to separate might lead todelamination of the laminate absorbent core.

Hence, upon expansion of the laminate absorbent core in the z-direction,the adhesive fibrous network is most likely prone to delaminate at thelocations, where the adhesive fibers of one layer got stuck and adheredto the adhesive fibers of the other layer. This tendency to adhesivefiber delamination is supported by the finding that, after the initialphase of laminate separation in the z-direction has required relativelyhigh forces, there is a relatively pronounced drop in the required forceafter the laminate layers have been separated by some millimeters (seegraph in FIG. 7): Once the fibrous network initially applied to thelower laminate layer has delaminated to a relatively large degree fromthe fibrous network initially applied to the upper laminate layer, theupper and lower laminate layer are relatively easy to separate, which isreflected by the considerably lower forces needed to separate thelaminate further compared to the initial high forces.

It is neither desirable that the laminate absorbent core requires veryhigh initial forces for laminate layer separation the z-direction, noris it desirable to have a drastic drop in the forces needed forseparation after an initial phase: The high forces required in theinitial phase may result in delayed liquid absorption and thus,increased risk of leakage. A significant drop of forces below a certainlevel may result in reduced immobilization of the superabsorbent polymermaterials comprised in the laminate absorbent core, as the fibrousnetwork, which is meant to immobilize the superabsorbent polymermaterial, is weakened, leading to delamination and reduced integrity ofthe laminate absorbent core.

Based on these insights gained by the inventors, laminate absorbentcores are needed, which, when subjected to the Laminate CompressionExtension Test described below, requires relatively low forces uponinitial separation of the laminate absorbent core in the z-direction(peak swelling restriction pressure). Also, the forces needed toseparate the laminate layers should not drop below a certain thresholdupon further separation (which would be an indication for a relativelyhigh degree of delamination) to ensure sufficient superabsorbent polymermaterial immobilization for laminate absorbent cores which are in thewet state (wherein a certain expansion and separation of the laminatelayers in the z-direction has occurred).

The laminate absorbent core of the invention fulfills theserequirements:

In the laminate absorbent core of the invention, the superabsorbentpolymer material and the fibrous layer of first adhesive is configuredsuch, that at least some of the adhesive fibers, which are adhered toand extending from one carrier substrate to the other in the z-directionof the laminate absorbent core, are enabled to take a longer pathcompared to the shortest, straight line between the upper and lowerlaminate layer. Moreover, it is desirable that a higher number ofadhesive fibers is attached both to the first and to the second carriersubstrate. These aspects can be facilitated especially by joining thefirst and second laminate layer such, that the superabsorbent polymermaterial is not distributed generally continuously between the upper andlower laminate layer but that interstices are formed where little or nosuperabsorbent polymer material is present. By doing so, at least someof the adhesive fibers can take a more inclined path between the firstand second carrier substrate (indicated as Y in FIGS. 2 and 3),resulting in a longer adhesive fiber extending between the first andsecond carrier substrate compared to adhesive fibers taking a straightpath.

By providing such longer distance between the locations wherein a givenadhesive fiber is attached to the first and second carrier substrate,the fibers can “stand up” and straighten up upon expansion the laminateabsorbent core in the z-direction. Compared to elongation of an adhesivefiber, which, as set out above, is required for adhesive fibers takingthe direct, shortest path between the first and second laminate layersin the dry, unexpanded laminate absorbent core, such straightening up ofadhesive fibers without the initial need for adhesive fiber elongationrequires considerably less force.

These findings are reconfirmed by Example 1 given below (see graph inFIG. 6): For laminate absorbent cores which have a structure as the oneexplained in detail above in the section “Absorbent Core” considerablyless forces are required for initial laminate layer separation (peakswelling restriction pressure) compared to currently available laminateabsorbent cores wherein superabsorbent polymer particles aresubstantially continuously supplied between the first and second carriersubstrate.

Also, a relatively high number of adhesive fibers appear to be attachedto both, the first and second carrier substrate, such that thedelamination tendency of the laminate absorbent core—when the core isfurther pulled apart—is reduced. This is reflected by the fact, that theforce needed to separate the laminate layers at 20 mm is higher inExample 1 compared to the Comparative Example 1. This so-called“Pressure at 20 mm” is the pressure exerted by the laminate absorbentcore when it has been pulled apart in the z-direction such that thethickness of the absorbent core (i.e. extension in z-direction 120 asshown in FIGS. 2 to 4) is 20 mm when subjected to the LaminateCompression Extension Test.

In embodiments having a second adhesive, as explained in detail above,the second adhesive may improve adhesion of the first adhesive to thecarrier substrate. The second adhesive is typically applied directlyonto the first and/or second carrier substrate such that the secondadhesive is positioned below any superabsorbent polymer material. Thefirst adhesive is thus—at least partly-attached to the carrier substrateindirectly via the second adhesive. However, a part of the firstadhesive may still be directly attached to the carrier substrate.

While in the Laminate Compression Extension Test described herein thecore is separated in z-direction in the dry state, the behavior of a wetlaminate absorbent will not differ significantly from the behavior inthe dry state. The adhesive fibers of the first adhesive adhere to eachother, to the first and second carrier substrate and to the optionalsecond adhesive, and they also adhere to the superabsorbent polymermaterial. However, as the superabsorbent polymer material gets wet andexpands, the attachment of the adhesive fibers to the superabsorbentpolymer material is weakened, as the adhesive strength between theadhesive fibers of the first adhesive and wet superabsorbent polymermaterial is lower compared to the adhesive strength between the adhesivefibers and dry superabsorbent polymer material. Hence, upon wetting andswelling of the superabsorbent polymer material, the adhesive fibers ofthe second adhesive will largely detach from the superabsorbent polymermaterial. Therefore, there is no significant difference betweenexpansion in z-direction in dry and wet state of the laminate absorbentcore: When expanding in the wet state, the adhesive fibers will detachfrom the swollen superabsorbent polymer material, and hence, thesuperabsorbent polymer material will not affect the behavior of theadhesive fibers. When expanding in the dry state, the adhesive fiberswill partly detach from the superabsorbent polymer material and theremaining superabsorbent polymer material, which remains attached to theadhesive fibers, will move together with the adhesive fibers. However,the adhesive fibers still entangle the superabsorbent polymer material,thereby facilitating immobilization of the superabsorbent polymermaterial.

Comparative Example 1

Pampers “Active fit” diapers as commercially available in Germany in May2011. Size 4 Comparative Example 2

Pampers “Baby Dry” diapers as commercially available in Germany in May2011. Size 4. (Note: The absorbent core of diaper contains airfelt withsuperabsorbent polymer particles mixed with the airfelt)

Example 1

Example 1 is a laminate absorbent core with two laminate layers, afirst, lower and a second, upper laminate layer.

Upper Laminate Layer

A 390 mm long and 165 mm wide nonwoven web (SMS, i.e.spunbond-meltblown-spunbond layers) made of polypropylene and having abasis weight of 10 g/m² was used as second upper carrier substrate. 5stripes of the second adhesive (hot melt adhesive) were applied in thelongitudinal direction, each stripe having a width of 2 mm and coveringa whole length of the product what is 390 mm. The distance between thecenter (referring to the width of the stripe) of two adjacent,neighboring second adhesive stripes was 20 mm. The basis weight of thesecond adhesive in each stripe was 116 g/m². The second adhesive is thesame material as the second adhesive in Comparative Example 1.

Next to each second adhesive stripe, a 8 mm wide and 360 mm long stripeof super absorbent polymer material is placed, such that the number ofsuperabsorbent polymer material stripes is 6. The superabsorbent polymeradhesive stripes are applied leaving a gap of 15 mm to front and backedge of the carrier substrate. The distance between the center(referring to the width of the stripe) of two adjacent, neighboringsuperabsorbent polymer material stripes is 20 mm, resulting in adistance between the center of the superabsorbent polymer materialstripe to the center of the neighboring second adhesive stripe of 10 mm.The superabsorbent polymer material is the same as the one applied inComparative Example 1. The overall amount of superabsorbent polymermaterial in the lower laminate layer is 10 g, which are evenlydistributed on the 6 superabsorbent polymer material stripes.

Subsequent to the application of the superabsorbent polymer materialstripes, a net of first adhesive is evenly applied, having an averagebasis weight of about 10 g/m² and a width of 108 mm, covering the wholelength of the product. The first adhesive is applied in the same way asin Comparative Example 1 and the first adhesive also consists of thesame material as the first adhesive of Comparative Example 1.

Lower Laminate Layer

A 390 mm long and 130 mm wide nonwoven web (SMS, i.e.spunbond-meltblown-spunbond layers) made of polypropylene and having abasis weight of 11 g/m² was used as first, lower carrier substrate.

6 stripes of the second adhesive (hot melt adhesive) were applied in thelongitudinal direction, each stripe having a width of 2 mm and coveringa whole length of the product what is 390 mm. The distance between thecenter (referring to the width of the stripe) of two adjacent,neighboring second adhesive stripes was 20 mm. The basis weight of thesecond adhesive in each stripe was 97 g/m². The second adhesive is thesame material as the second adhesive in Comparative Example 1.

Next to each second adhesive stripe, a 8 mm wide and 360 mm long stripeof superabsorbent polymer material is placed, such that the number ofsuperabsorbent polymer material stripes is 5. The superabsorbent polymeradhesive stripes are applied leaving a gap of 15 mm to front and backedge of the carrier substrate. The distance between the center(referring to the width of the stripe) of two adjacent, neighboringsuperabsorbent polymer material stripes is 20 mm, resulting in adistance between the center of the superabsorbent polymer materialstripe to the center of the neighboring second adhesive stripe of 10 mm.The superabsorbent polymer material is the same as the one applied inComparative Example 1. The overall amount of superabsorbent polymermaterial in the lower laminate layer is 10 g, which are evenlydistributed on the 5 superabsorbent polymer material stripes.

Subsequent to the application of the superabsorbent polymer materialstripes, a net of first adhesive is evenly applied, having an averagebasis weight of about 10 g/m² and a width of 108 mm, covering the wholelength of the product. The first adhesive is applied in the same way asin Comparative Example 1 and the first adhesive also consists of thesame material as the first adhesive of Comparative Example 1.

Combination of Upper and Lower Laminate Layer

The upper and lower laminate layers are placed together such that thesurfaces of both carrier substrates, which not covered by superabsorbentpolymer material are facing outwardly. Thereby the laminate absorbentcore is formed with the superabsorbent polymer material (and the firstand second adhesive) encased between the first and second carriersubstrate.

When the two layers are combined, the center (referring to the width) ofeach of the top superabsorbent polymer material stripes of the upperlaminate layer bars overlays and contacts the center of the respectivesecond adhesive stripe of the lower laminate layer and vice versa.Hence, each superabsorbent polymer material stripe of the upper layer isplaced centrally in the respective gap between two superabsorbentpolymer material stripes of the lower laminate layer and vice versa. Thesuperabsorbent polymer material stripes of one laminate layer do nottouch the superabsorbent polymer material stripes of the respectiveother laminate layer.

The longitudinal edges of the second, upper carrier substrate of theupper laminate layer is folded over along the longitudinal side edges ofthe first, lower carrier substrate of the lower laminate layer onto thesurface of the first, lower carrier substrate which, when the laminateabsorbent core is put into an absorbent article, is facing towards thegarment of the wearer (when the article is in use). Upon folding, alsothe first, lower carrier substrate is slightly folded over outwardly,such that the final width of the laminate absorbent core is 120 mm. Thefolded areas of the both carrier substrates are adhesively attached andthus fixed in their folded configuration.

The Example and the Comparative Examples were subjected to the LaminateCompression Extension Test Method to measure the peak swellingrestriction pressure and the swelling restriction pressure at 20 mm.

Laminate Compression Extension Test

The method determines the swelling restriction pressure that is appliedon the superabsorbent polymer material by the first adhesive in thelaminate absorbent core in dependency of separation of the laminateabsorbent core in the z-direction.

Equipment

-   -   Analytical Balance with an accuracy of at least 0.01 g.    -   Vernier caliper with a length of at least 100 mm and a        sensitivity resolution of ±0.05 mm    -   Chamber capable to be controlled up to a temperature of 37° C.        (+/−1° C.)    -   Vertical Single column Zwick Tensile Tester machine inside the        temperature chamber with Zwick Roell Load cell which has maximum        compression force of 50 N with force accuracy of 0.3% and        distance accuracy of 0.15% or equivalent instrument    -   Double sided adhesive tape from teas SE “tesa Bastelband        beidseitig klebend” 56665-0001, 2.75 m×38 mm    -   Two T-shaped sample holders made out of Plexiglas    -   Elastic natural rubber foam with 3 mm thickness to cover surface        of T-shaped sample holders: Supplier: KKT GmbH, Siegen, Germany.        Material description: “Zellkautschukstreifen EPDM Schwarz,        einseitig selbstklebend als Montagehilfe mit Klebertyp VI in 10        m Rollen 90×3 mm”    -   Alfa Hydraulic Sample Cutter. E.g. from, Thwing-Albert        Instrument Company, Alfa hydraulic precision sample cutter,        serial no: 4450, 19154 catalog 240-10 or equivalent, with 60 mm        diameter circular cutter, e.g. Karl Reichert GmbH, Rheinstr. 5,        86955 Pirmasens    -   Marker (e.g. ball point pen, fine tip)    -   Metal Ruler traceable to NIST, DIN, JIS or other comparable        national standard, graduated in mm.    -   Computer connected with Zwick Tensile Tester machine and        installed with acquisition program ‘testXpert’ software version        10.0, software provider: Zwick GmbH & Co, D-89079 Ulm, or        equivalent.

Test Setup

FIG. 5 shows the setup of the Zwick Tensile Tester 500 as used for theLaminate Compression Extension Test.

The system consists of the following main parts:

Upper sample holder 510 made of Plexiglas, movable up and down

Lower sample holder 520 made of Plexiglas

Elastic natural rubber foam 530 used as damping adhesively attached toboth sample holders,

covered with double sided adhesive tape 540

Load Cell measuring compression and extension in the range of −50 N-50 N

The upper and lower sample holder need to be large enough to support andaccommodate the complete sample.

Method

The test sample can be either prepared out of a complete absorbentarticle or, alternatively, can be prepared from a laminate absorbentcore which has not been incorporated into an absorbent article before.(As illustrated by Comparative Example 2, the method can generally alsobe applied to absorbent cores which are not laminate absorbent cores butwhich comprise a mixture of superabsorbent polymer material withairfelt).

If the test sample is taken from the laminate absorbent core which haspreviously been incorporated into an laminate absorbent article, thefollowing procedure needs to be followed to isolate the laminateabsorbent core from the absorbent article: All layers of the absorbentarticle above and below the laminate absorbent core are carefullyremoved. The laminate absorbent core of the invention has an upper and alower carrier substrate (typically a nonwoven web, a tissue or a film)with the superabsorbent polymer material encased in between thesecarrier substrates. Hence, the laminate absorbent core can be clearlyidentified in absorbent articles encompassed by the invention.

If any layers are strongly attached to the laminate absorbent core suchthat they only be partly removed, those layers should be removed to theextent possible without damaging or destroying the laminate absorbentcore. If a layer cannot be removed at all due to strong attachment tothe laminate absorbent core, this layer will remain on the laminateabsorbent core for the further test procedure. The strength of thisattachment will be stronger compared to the forces measured in themethod herein and therefore this/these layer(s) will have no significantinfluence on the data obtained.

On the longitudinal axis of the laminate absorbent core mark a firstpoint at a distance of 145 mm from the front laminate absorbent coreedge and a second mark at a distance of 205 mm from front laminateabsorbent core edge. A 60 mm diameter circle is cut out between thesetwo marks with the center of the circle being on the longitudinal axisof the laminate absorbent core. This circular cut out represents thetest sample.

Both Plexiglas sample holders are covered with the elastic naturalrubber foam. Double sided tape is attached on the natural rubber foam ofboth Plexiglas sample holders over the whole surface of the test sampleholders.

The test sample is attached to the double sided tape of the lower sampleholder with the lower carrier substrate of the test sample facingdownwards (i.e. the lower carrier substrate is attached to the sampleholder).

The lower sample holder is then put in the lower clamp of the ZwickTensile Tester apparatus and the upper sample holder is put in the upperclamp of the Zwick Machine such that the upper and lower sample holderare fully congruent with each other.

The complete set up including the Zwick Tensile Tester apparatus withthe test sample is heated to a temperature of 37° C. in the climatechamber at a relative humidity of 50%+/−5%. Once the temperature isreached, the temperature and relative humidity is maintained for 5minutes before the further method steps are carried out. The temperatureand relative humidity are also maintained throughout the followingmethod steps.

The upper sample holder is moved down at a speed of 20 mm/min until acompression of 50 N is reached. Thereby, reliable attachment of thesample to the upper and lower sample holder is achieved.

Then the upper sample holder is moved up at a speed of 2.5 mm/min untila compression of 5.844 N is reached. The distance between the rubberfoams on the upper and lower sample holder represents the caliper of thesample when compressed with a force of 5.844 N. (The initial caliper ofthe sample is the caliper without any force being applied on the sample.This initial caliper of the sample represents the caliper of thelaminate absorbent core of the invention).

-   -   Now the upper sample holder is moved up further at a speed of        0.085 mm/second until a sample caliper of 11.78 mm(=distance        between upper and lower sample holder) is reached.    -   Immediately thereafter, the upper sample holder is moved up at a        speed of 0.023 mm/second until a sample caliper of 15.96        mm(=distance between upper and lower sample holder) is reached.    -   Immediately thereafter, the upper sample holder is moved up at a        speed of 0.009 mm/second until a sample caliper of 18.63        mm(=distance between upper and lower sample holder) is reached.    -   Immediately thereafter, the upper sample holder is moved up at a        speed of 0.003 mm/second until a sample caliper of 20.32        mm(=distance between upper and lower sample holder) is reached.

At the end of the test, upper sample holder is moved further upwards toremove the sample and sample holders. The test is then stopped. Thetensile forces are measured continuously during the above stepsindicated with bullet points.

The software for the acquisition program ‘testXpert’ inter alia providesthe data on Standard Force [N] and LE channel 550 [mm]. The LE channeldata is set to represent the distance between the rubber foams of theupper and lower sample holder and thus the caliper of the sample. Toobtain the pressure in [N/m²] the Standard Force values in [N] aredivided by the area of the test sample, that is calculated to □*(0.03m)2=0.0028 N/m².

The Peak Pressure is the highest pressure value within a caliper rangeup to 20 mm. For the pressure at 20 mm caliper the pressure value istaken for the caliper first reaching 20 mm. Both values are reported.

Results: Peak Swelling Restriction Pressure and the Swelling RestrictionPressure at 20 mm

The diagrams showing the caliper [mm] of the test samples vs. thepressure [N/m²] are depicted in FIGS. 6, 7 and 8.

Initial Peak Swelling Swelling (Peak sample Restriction RestrictionPressure)/ caliper Pressure Pressure at (Pressure at [mm] [N/m²] 20 mm[N/m²] 20 mm) Example 1 2.5 226 57 4.00 Comparative 2.5 788 20 39.3Example 1 Comparative 5.2 33 12 2.79 Example 2

The results show that a laminate absorbent core of Example 1 of theinvention has a significantly reduced peak pressure versus thecommercially available Comparative Example 1 wherein the superabsorbentpolymer material is distributed substantially continuously within theabsorbent core.

Also, after separation to 20 mm in the z-direction, the pressure ofExample 1 of the invention is significantly higher versus theComparative Example 1, indicating that considerably lesser delaminationwithin the absorbent core has occurred.

The ratio of Peak Pressure to Pressure at 20 mm is also considerablylower for Example 1 of the invention compared to Comparative Example 1.This reflects that a much more uniform tensile force is needed toseparate the laminate layers versus the Comparative Example 1, where avery high peak pressure is followed by a steep drop in the pressureapplied when further separating the layers.

Comparative Example 2 shows that in a conventional airfelt-containingabsorbent article the force needed to separate the upper carriersubstrate from the lower carrier substrate is considerably less comparedto a laminate absorbent core having very high amount of superabsorbentpolymer material. The absorbent core of Comparative Example 2 is not alaminate absorbent core with two layers. Instead, the absorbent core ofComparative Example 2 comprises a mixture of cellulose fibers andsuperabsorbent polymer particles, which are encased by nonwoven webs.Hence, the superabsorbent polymer particles are not immobilized byadhesive but are held in place in the interstices between the cellulosefibers. However, the cellulose fibers can be pulled apart in thez-direction of the absorbent core with little forces needed, which isreflected by the data obtained.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An absorbent core comprising: a first carriersubstrate and a second carrier substrate; a discontinuous layer ofsuperabsorbent polymer material disposed between the first and secondcarrier substrates, comprising a plurality of superabsorbent materialstripes; two of the stripes being separated by an interstice; whereinthe interstice comprises little or no superabsorbent polymer materialand wherein the interstice extends from the first carrier substrate tothe second carrier substrate.
 2. The absorbent core according to claim 1wherein: the superabsorbent polymer material forms multiple stripes onthe first carrier substrate to form a first lower laminate layer, andthe superabsorbent polymer material forms multiple stripes on the secondcarrier substrates to form a second, upper laminate layer, the stripeson each layer being spaced apart from each other to form gaps betweenneighboring stripes, the second laminate layer being positioned on thefirst laminate layer with the first and second carrier substrates facingoutwardly, such that the superabsorbent polymer material stripes of thesecond laminate layer are overlaying the gaps formed in the firstlaminate layer and the superabsorbent polymer material stripes of thefirst laminate layer are overlaying the gaps formed in the secondlaminate layer; and wherein the interstice is formed by one of the gapsbeing wider than the superabsorbent polymer stripe lying above or belowsaid one of the gaps.
 3. The absorbent core according to claim 2 whereinthe one of the gaps is at least 2 mm wider than the superabsorbentpolymer stripe lying above or below said one of the gaps.
 4. Theabsorbent core according to claim 2 wherein the interstice is formed byone of the gaps in the first laminate layer being wider than thesuperabsorbent polymer material stripe of the second laminate layerlying above the gap.
 5. The absorbent core according to claim 2, whereinthe interstice is formed by one of the gaps in second laminate layerbeing wider than the superabsorbent polymer material stripe of the firstlaminate layer lying below the gap.
 6. The absorbent core according toclaim 1 wherein the two superabsorbent material stripes are straight. 7.The absorbent core according to claim 1, wherein the superabsorbentpolymer material is at least partially immobilized by an adhesive. 8.The absorbent core according to claim 2, wherein a second adhesive isapplied onto the first and second carrier substrate such that the secondadhesive is applied in the gaps between the superabsorbent polymermaterial stripes and below the superabsorbent polymer material stripesof each laminate layer.
 9. The absorbent core according to claim 1comprising less than 5% by weight of cellulose fibers.
 10. The absorbentcore according to claim 1 wherein the material stripes extendlongitudinally.
 11. The absorbent core according to claim 1 wherein thematerial stripes extend laterally.
 12. An absorbent article comprising atopsheet, backsheet and an absorbent core, wherein the absorbent corecomprises: a first carrier substrate and a second carrier substrate; adiscontinuous layer of superabsorbent polymer material disposed betweenthe first and second carrier substrates, comprising a plurality ofsuperabsorbent material stripes; two of the superabsorbent materialstripes being separated by a interstice; wherein the intersticecomprises little or no superabsorbent polymer material and wherein theinterstice extends from the first carrier substrate to the secondcarrier substrate.